Electrical device



Jan. 17, 1939. W. R KOCH 2,144,337

ELECTRICAL DEVICE AMPLlF/ER Patent Jan, 17, 1939 UNIED YSTATES PATENTOFFICE 2,144,337 ELECTRICAL DEVICE Winiield R. Koch, Camden, N. J.,assigner to Radio Corporation of America, a. corporation of Delaware Myinvention relates to electric wave shaping apparatus and particularly toa method of and means for producing an electric wave of the desired waveshape by deflecting a cathode ray.

Various forms of apparatus have been employed for producing electricwaves having a wave shape other than that of a sine wave. Such apparatusgenerally includes thermionic vacuum tubes, iron core inductances, gasdischarge tubes, or the like. It is often diicult to obtain exactly thedesired wave shape when employing such apparatus.

An object of my invention is to provide an improved method of and meansfor producing electric waves of any desired wave shape. A further objectof my invention is to provide improved apparatus including a cathode raytube for producing an electric wave of non-sinusoidal wave form.

In one embodiment of my invention a cathode ray tube is so designed thatthe cathode ray is spread out in a plane or line instead of beingconfined to a, ray of small diameter, as is customary in cathode raytubes. This plane or line of electrons is projected towards a platehaving a shape which preferably conforms to the wave shape desired, andthe cathode ray is deected along this plate whereby the number ofelectrons striking the plate varies from instant to instant to produce aow of current having the said wave shape.

One of several other embodiments of the invention includes a cathode raytube having a fluorescent screen and further includes a photo-electriccell and a mask positioned between the fluorescent screen and thephoto-electric cell. The mask has an opening therein which preferablyhas a shape which conforms to the wave shape of the desired electricwave whereby the amount of light reaching the photo-electric cell variesfrom instant to instant as the cathode ray is deflected across thefluorescent screen.

Other objects, features and advantages of the invention will appear fromthe following description taken in connection with the accompanyingdrawings, in which y Figures 1, 2 and 3 are schematic and circuitdiagrams of three embodiments of my invention,

Figures 4, 5 and 6 are end views oi the mask and cathode ray tube shownin Figure 3, the three different views showing masks with threedifferent lshaped openings,

age of the proper value supplied thereto. If de- Fig. 8 is a blockdiagram of a radio transmitter utilizing my invention.

' Referring to Fig. 1, the apparatus includes a cathode ray tubecomprising an evacuated envelope I, an indirectly heated cathode 2, acontrol 5 grid 3, a rst anode 4 and a second anode or signal plate 6,which is specially shaped as above mentioned. Preferably another plate Iis provided adjacent to the plate 6, as illustrated, for the purpose ofaiding in the acceleration of the electrons and for providing a returnpath for electrons which do not strike the signal plate 6.

A screen grid 8 and a suppressor grid 9 may be provided which serve thesame purpose as like grids in conventional amplier tubes. 15

In the embodiment illustrated, the cathode ray is spread out into aplane or line at right angles to the plane of the paper by means of twodeflecting or focusing plates I I which have a fixed voltsired, the sameresults may be accomplished by properly designing the electron gun andomitting the focusing plates.

Suitable positive voltages are supplied to the first anode 4, the grids8 and 9 and the plates 6 and i from a suitable source such as a batteryindicated at I2. A negative biasing voltage is supplied to the controlgrid 3 from a suitable source such as a battery I3. l

Voltage is supplied to the signal generating plate 6 through an outputresistor I4 across which the desired signal voltage appears. This signalvoltage may be supplied through a coupling condenser I 6 to a suitableamplifier I1.

The operation of this apparatus depends upon the fact that as theelectron stream, indicated at I8 by the dotted lines, is deflected in avertical plane by suitable deecting devices such as deflecting platesI9, the number of electrons striking the signal plate 6 and passingthrough the output resistor I4` depends upon the angle of deflection ofthe electron stream. For example, with the electron stream in theposition indicated on the drawings, the amount of current flowingthrough the output resistor I4 is greater than when the electron streamis deflected further from the center of the tube and it is less than'when the electron stream is deflected towards the center of the tube.Obviously, the current iiow through the output resistor I4 and,therefore, the voltage applied to the grid of the amplifier tube I1depends upon the shape of the signal plate 6 and the wave shape of thevoltage applied to the deiiecting plates I9. The deilecting voltage,preferably, is either sinusoidal or saw-tooth in wave form.

Referringto ,2 of the drawings. there is illustrated a cathode ray tube2i which'is con-"f ventional in construction except for certain modifyilcations which rwill be, described. The tube includes the usualelectron gun 22 and second anode 23, ,thev electron beam being focusedelectrof statically. As, in ,the embodiment ofthe invention shown inFig. 1, a signal plate 24 isy provided which is positioned in the pathoi' the electron beam yand shaped in accordance with thewave form of thesignal wave to be generated. yThe f signal plate 24 is connected throughan output resistor 2,6 to ground whereby a ilow of current is producedthrough the resistor whichfis propor-r tional to the number of electronsstriking the This elecelectrons traverse the signal plate 24'along ayliney as indicated by the dotted lines 28. In order to yproducethedesired 'signal wave, the electron beam is also deflected in a'planesubstantially at right angles to the ilrst deflection by means ofotherdeflectin plates 23 or other suitable deflecting devices. f f f f ff -It will be understood that the operation is substantially the same asthe operationof the device previously described. 'The'mainfdiilerence inoperation is that, while the electron beam is being deflected verticallyby means of the low frequency deflecting plates 29,y impulses of energyare being applied to the signal plate 24 at the frequency op thedeection produced by the other deilecting plates y21.r f 'Because ofthis, ,ther signal voltage appearing across the resistor 26 is suppliedto the amplifier tube l1 through a filter 3| which may consit of aninductance coil 32 and shunt condensers 33 and 34. The filter 3l isgiven a time constant which is greater than the period of the deilecting.wave applied to the high frequency deflecting plates 21 whereby anuninterrupted voltage is applied to the grid of tube I1, the magnitudecf the voltage changing in consonance with the low frequency deilectionof the cathode beam and in accordance with the shape of the signal plate24.

Deilecting waves of any desired Wave form may be applied to thedeilecting plates but in general either sine waves or saw-tooth wavesare preferred.

Referring to Fig. 3, the cathode ray tube 36 may be the same as the tube2| shown in Fig. 2, except that a fluorescent screen 31 is provided atthe end of the tube. In this embodiment of the invention, it is desiredto produce a line of light on the fluorescent screen and to deflect thisline of light behind a mask having an opening therein whereby the amountof light passing through the mask depends upon the shape of the opening.In the drawings, a photo-electric cell is indicated at 38 for receivinglight from the uorescent screen 31. A mask 39 and a suitable opticalsystem 4| are located between the photo-electric cell 38 and the screen31. One form of mask is shown in Fig. 4, this being an end view of themask 39 and cathode ray tube 36.

In the particular embodiment shown in Figs. 3 and 4, the electron beamis deflected vertically at a comparatively high frequency by deflectingplates 42; whereby,y as the electron beam is deilected more slowly inthe horizontal plane by the deilecting plates 43, a vertical line oflight moves across themask opening. As the line of light moves from thecenter of the tube to either side, the amount of light passing throughthe photo-electric cell 38 increases. be provided in the output circuitof the photof electric ycell y38,fas,indicated, in order to integratethe light impulses caused by the high frequency f f deection oftheelectron beam. It will be understood that the necessary'filter actionmay be provided in the photo-electric cell amplifier I6 itself, f

if desired. As in the apparatus rshown in Fig. 2, rtheillter'requirements are that the time constant of the filter be greaterthan the period'of' high frequency deflection.

,By yproperly shaping the opening of the mask, any desired alteration inwave shape can' be secured. Thus, if"square law operation isdesired.feach sldeof the openingof the mask 39 is given a paraboliccurve as' shown rinr Fig. 4.' With this mask and with a saw-toothvoltage applied to ,theme11 frequency deilecting plates 42 and a sinewave voltage, indicated' at '45 in' Fig. 7, apa

plied to the low frequency deflecting plates 43,

, ,the yresulting signal supplied to the amplifier 46 has the wave shapeindicated' by' the'curve 41 in Fig. 7. It will be noted that this signalis sinusy roidal in wave form and has double the frequency of the signalapplied to the low'frequeney deilecting plates 43, this being the signalwhich is re-shaped.

By using a mask "with an opening having the f lating audio wave at atransmitter may be given a square root shape so that with alinearmodulator at the transmitter the receiver may have a square law detectorwithout any resulting distortion. With a high frequency saw-tooth waveapplied to the plates 42 and with the modulating sine Wave applied tothe plates 43, the resulting wave having the square root shape is shownby the curve 50 in Fig. 7.

'I'he diagram in Fig. 8 shows how such a wave shaper may be vincluded ina radio transmitter. A wave shaper of the type above-described isindicated at 43.

By making the opening in a mask 5I of the shape shown in Fig. 6 thecathode ray tube may be employed to give linear detection by applyingthe radio or intermediate frequency voltages to the deecting plates 43.'I'he wave form of the signal applied to the ampliiier 46 when the maskis of the form shown in Fig. 6 isindicated by the curve 52 in Fig. 7. Itwill be apparent that this is a rectified'sine wave. f

It may be noted that if the uorescent material of the fluorescent screencontinues to glow after the bombardment stops, the slope of the decaycurve should be steep and the shape of the opening in the mask may haveto be modified.

From the foregoing description, it will be apparent that various othermodifications may be made in my invention without departing from thespirit and scope thereof and I desire, therefore, that only suchlimitations shall be imposed thereon as are necessitated by the priorart and are set forth in the appended claims.

I claim as my invention:

1. An electrical wave generator comprising an electric discharge tubehaving means for producing a stream of electrons spread out in a certainyOpeningincreases, whereby the output of the Afilter44'sho'u1dy f planewhereby their cross-section is a line, a iluorescent screen positionedin the path of said electrons whereby a line of light is formed thereon,a photo-electric device positioned to receive said' light, a maskpositioned between .said fluorescent screen and said photo-electricdevice,

said mask having an opening therein which is ,f

shaped in accordance with the desired wave shape of the electrical waveto be generated, and means for defiecting said stream of electronssubstantially at right angles to said certain plane whereby the amountof light reaching said photo-electric device from said line of lightvaries in accordance with the shapey of said mask opening.

2. An electrical wave generator comprising an electric discharge tubehaving means for producing a beam of electrons, a signal plate ofelectrically conducting material shaped in accordance with the desiredwave shape of the electrical wave to be generated, means for deilectingsaid electron beam at a comparatively high frequency in a certain planewhereby said electrons strike said signal plate along a line, means fordeilecting said electron beam periodically at a comparatively lowfrequency and substantially at right angles to said line, whereby thenumber of electrons striking said plate is varied, and means including aillter for taking the resulting signal from said plate, said lter havinga time constant which is larger than a period of said high frequencydeflection.

3. An electrical wave generator comprising an electric discharge tubehaving means for producing a beam of electrons, means for deecting saidelectrons in a certain plane at a comparatively high frequency, auorescent screen positioned in the path of said electrons whereby a lineof light is formed thereon, a photo-electric device positioned toreceive said light, a mask positioned between said iiuorescent screenand said photoelectric device, said mask having an opening therein whichis shaped in accordance with the desired wave shape of the electricalwave to be generated, means for deiiecting said'beam of electronssubstantially at right angles to said certain plane whereby the amountof light reaching said photo-electric device from said line of lightvaries in accordance with the shape of said mask opening, and an outputcircuit for said photo-electric device, said output circuit having atime constant which is larger than the period of one of said highfrequency oscillations.

4. An electrical wave generator comprising an electric discharge tubehaving means for producing a beam of electrons, means for deecting saidbeam in a certain plane at a comparatively high frequency, meansincluding a screen structure so positioned in the path of said beam thatsaid deection causes said beam to trace a line thereon for generating inresponse to deflection of said beam at right angles to said certainplane a signal voltage having a. wave shape determined i by the outlineof said screen structure, means for deecting said beam at right anglesto said certain plane at a comparatively low frequency, an outputcircuit including a filter having a time constant which is larger thanthe period of one of said high frequency oscillations, and means forsupplying said signal voltage to said output circuit.

5. An electrical wave generator comprising an electric discharge tubehaving means for producing a stream of electrons effectively spread outin a certain plane whereby their effective cross-section is a line,means for deflecting said beam periodically in a plane substantially atright angles to said certain plane in accordance with an electricalfield, and means including a screen structure having an area. bounded byan edge parabolic in shape and by an opposite edge which is a straightline for making successively changing fractions of said line ofelectrons eilective to produce signals during said deflection, saidscreen structure being located with said straight line edge at rightangles to said certain plane whereby the wave shape of said signals isthe square root DISCLAIMER -2,l44,337.-Win eld R. Koch, Camden, N. J.ELECTRICAL DEVICE. Patent dated' January 17, 1939. Disclaimer ledNovember 22, 1939, by the asslgnee,

Radio Corporation of America.

Hereby enters this disclaimer to claims 2 and 4 in said specification.

[Qcicl Gazette December 12, 1.939.]

